Fri November 4, 2011

The sun is out, but it's cold ... what's happening?

We're getting some beautiful sunrises and until we set our clocks back, we’re all up to see them!

Today and Saturday we’ll get some of those morning sprinkles, but the afternoons clear off with temperatures hitting around 50, and then starting on Saturday afternoon we get some “very interesting” weather for the Northwest, says KPLU’s weather expert Cliff Mass.

“From roughly Tacoma north it is going to be dry and some partly cloudy skies, but farther south from southwest Oregon and along the coast there is going to be some showers and clouds -- so two different weather situations,” Mass says.

This pattern of a cold air mass is keeping our high temperatures in the low 50s. Through next week, the storms that come in from the ocean will hit the coast and get pushed down into California, where our southern neighbors will be wet and cold!

No need for freezing temperatures to get snow

We start hearing a lot this time of year about “the freezing level.” In fact, we had snow this week in the mountains. But, as Mass explains, the freezing level and snow level are not the same.

Freezing level is straightforward, he says. It’s the altitude where the temperature is 32. If warm air blows in, the freezing level might rise to 8,000 feet, and then another storm comes and it falls again to 2,000 feet, or even sea level.

Snow level is at a lower altitude than freezing level – about 1,000 feet lower.

“Nearly all our precipitation starts as snow aloft. It falls down, hits the freezing level and starts melting. [But] it doesn’t melt immediately. It takes about a thousand feet for that snow to melt into rain.”